The present invention relates to a method of sampling wobble components without using a sample/hold circuit and a disk drive unit executing said method.
Time data and position data of optical disks, e.g., CD-R/RW, DVD-R/RW, are recorded by a wobble groove of a pregroove of the disk. Position data of the wobble groove is known by measuring luminous power of reflected laser beams, which are emitted from laser diodes and reflected at the optical disk. Luminous power of laser beams for reading data from the optical disk is different from that for writing data thereon, therefore luminous power of the reflected laser beams for reading data are also different from that for writing data. Identification data, which identify the laser beams for reading or writing data, and data of the wobble components are included in the reflected laser beams. To sample the wobble components from low power laser beams for reading data and high power laser beams for writing data, flexures caused by difference of the luminous power between the reflected low power laser beams and the reflected high power laser beams must be shaped when the wobble components are sampled. However, a complex mechanism must be required to shape the flexures, so that the conventional disk drive unit must have a complex structure.
To omit the step of shaping the flexures of the wobble components which are caused by the difference of the luminous power of the reflected laser beams, the wobble components are sampled from the low power laser beams only, so that the structure of the disk drive unit can be simple. When data are written by the high power laser beams, the wobble components of the low power laser beams are used. In this drive unit, the wobble components are treated by a sample/hold circuit.
In the case of treating the wobble components by the sample/hold circuit, the wobble components are sampled from the low power reflected laser beams for reading data from the disk. Electric signals indicating the wobble components charge a capacitor. On the other hand, when data are written on the disk by the high power laser beams, the capacitor discharge the electric signals so as to hold the wobble components of the low power laser beams for reading data. Therefore, the wobble components can be known while writing data.
In the sample/hold circuit, the wobble components are treated by charging and discharging the capacitor. However, it takes a long time to write data on the disk due to charging time, etc. So it is difficult to realize a disk drive unit capable of writing data in a short time.
Another conventional drive unit has a dividing circuit for sampling the wobble components instead of the sample/hold circuit. However, the dividing circuit cannot be actuated by one electric source, its frequency characteristics are not good, and it is expensive. Therefore, the disk drive unit including the dividing circuit is not useful.
An object of the present invention is to provide a method of sampling wobble components which is capable of realizing a disk drive unit, which can write data at high speed, and reducing manufacturing cost of the disk drive unit.
Another object is to provide a disk drive unit executing said method.
To achieve the objects, the present invention has following structures.
In the method of the present invention, wobble components are sampled from laser beams reflected from an optical disk so as to write data on the optical disk, and the laser beams are low power laser beams for reading data and high power laser beams for writing data,.
The method of the present invention is characterized in that the wobble components of the reflected low power laser beams and the reflected high power laser beams are continuously sampled.
In the method, one longitudinal edge of a wobble groove of the optical disk may be detected by a first photo diode for detecting first reflected laser beams, and the other longitudinal edge thereof may be detected by a second photo diode for detecting second reflected laser beams, wherein the first and second reflected laser beams may be processed so as to sample the wobble components.
By the method of the present invention, various kinds of noise included in signals of the sampled wobble components can be removed.
The disk drive unit, in which wobble components are sampled from laser beams reflected from an optical disk so as to write data on the optical disk, is characterized in,
that the laser beams are low power laser beamed for reading data and high power laser beamed for writing data, and
that the wobble components of the reflected low power laser beams and the reflected high power laser beams are continuously sampled.
By employing this structure, the wobble components can be sampled without using a sample/hold circuit, so that high speed operation of the disk drive unit can be realized.
Further, the disk drive unit, in which wobble components are sampled from laser beams reflected from an optical disk so as to write data on the optical disk, comprises:
a first photo diode for detecting one longitudinal edge of a wobble groove of the optical disk;
a second photo diode for detecting the other longitudinal edge of the wobble groove;
a differential amplifier to which signals are sent from the first and second photo diodes receiving the reflected laser beams, the differential amplifier shaping a flexure caused by difference of luminous power between low power laser beams of the reflected laser beams, which are used for reading data, and high power laser beams thereof, which are used for writing data, and sampling the wobble components only;
a noise removing circuit removing noise from the wobble components sampled by the differential amplifier; and
a comparator digitizing the wobble components from which the noise has been removed by the noise removing circuit.
With this structure, flexures and noise included in signals of the sampled wobble components can be removed, and high speed operation can be realized due to no sample/hold circuit.